In the field of commercial colour printing, the printed product should ideally conform as closely as possible to the design as created and visualized by the graphic designer. Because of the complexity of colour printing processes, there are myriad variables which can and will affect the colour and appearance of the printed product and thus, if not accounted for and carefully controlled, yield printed product which does not conform to the graphic designer's vision. Such variables may, for example in a flexography printing process, include:    a. ink properties, such as:            colour        viscosity        opacity/transparency        interaction of one ink with another (e.g. ink trap)        ink system used (i.e. the physical ingredients used in the ink emulsion selected according to the application—e.g. ingredients or additives to provide UV resistance)        which can all affect the spread and appearance of the ink on a print substrate (e.g. paper, cardboard, plastic, all of various types). Ink properties can change from supplier to supplier, from batch to batch, according to environmental conditions, or even with the passage of time.            b. substrate properties, such as:            colour        absorbency        porosity        surface finish        which can all affect the adherence and spread of ink, and thus its appearance, on the substrate.            c. printing plate properties, such as:            plate material (e.g. hardness, resilience, surface finish)        plate preparation processes, which can affect the properties of the plate material as well as process the plate to define the image to be printed (e.g. in flexography, by removal of plate material to define the relief portions defining the image)        plate backing or mounting material (e.g. the hardness and resilience of a particular “sticky back” mounting material to be used)        which can all affect adherence of ink to the printing plate and/or ink release from the plate and/or the ability to transfer ink to the substrate.            d. ink application system properties, such as:            analox roller selection (e.g. line screen and ink volume)        doctor blade selection and settings        which can all affect the amount of ink applied to the printing plate and thus the amount of ink ultimately transferred to the substrate.            e. printing processes, such as:            press speed (which affects ink drying time between the application of ink colours and contact time between plate and substrate thus affecting the amount of ink transferred)        printing plate pressure (which affects the amount of ink transferred to the substrate).        
In addition to the above, errors of all types, including failure to maintain good housekeeping practices, may lead to unintended contamination of ink or substrate or improper application of ink to substrate.
The proper selection of materials, equipment and settings will result in a print run in which the ink on the finished printed product will have satisfactory properties, such as:                ink colour (i.e. satisfactory spectral measurement in either LAB or LCH)        colour density (i.e. satisfactory ink film thickness)        dot gain (i.e. satisfactory ink dot width after taking into account the percentage increase or decrease, i.e. “gain”, of an ink dot from printing plate to final printed product) and        gray balance (i.e. satisfactory layering of ink film colours).        
Provided that the print variables are carefully controlled for a particular printing press, it should be possible for a printing press to deliver consistent products over time, or from print run to print run or even from job to job. To assist in controlling press performance, it is known to require a press to print a calibration image under production conditions. When the printed calibration image is satisfactory, the values for all of the print variables are recorded in what is known as a press “fingerprint”. In the event that a future print from the same press appears not to be satisfactory, the fingerprint will be available as a standard against which the values of the print variables at the time of the future print may be compared. In this way, a measured assessment may be made as to whether and which and by how much any print variables may have changed, so that appropriate corrective action may be taken.
The standard against which a particular printed product is assessed is a hard copy document known as a “contract proof”. This document has been approved by both the customer and the commercial printer as representing the visual standard which the printed products must match as closely as possible. In current printing practice, contract proofs are prepared from electronic files of the artwork to be printed by a machine known as a dot proofer, for example as sold under the trademarks LATRAN PREDICTION or KODAK APPROVAL. A dot proofer prints the image to be printed on the press by simulating printed ink dots at an appropriate resolution on a carrier sheet and then applies this image to the relevant substrate. The result is a prototype document which the printing press should be able to match. The final version of the electronic file from which the contract proof was printed is sometimes known as an “electronic soft proof”.
In current practice, printing plates are prepared by, or supplied to a commercial printer, along with the contract proof. The printer will set up its printing press in a manner which the printer believes will yield a printed product which will closely match the contract proof. Setting-up a printing press is an iterative process, wherein the printer will adjust at least some of the variables mentioned above to arrive at a printed product which the printer believes does match the contract proof.
Before proceeding with a print run, a printer will require the customer to authorize the print run to proceed. In this authorization process, the customer's representative will be supplied with a sample of the printed product printed by the printing press under production conditions. The customer visually compares this physical specimen, known as a “press pull”, to the physical contract proof. If the press pull appears to match the contract proof in all significant respects, the customer's representative will approve the press run to proceed.
If the customer's representative believes that the press pull differs in significant respects from the contract proof, then the printer will be required to adjust the printing variables further and run another press pull. The process will be repeated until the customer's representative is satisfied.
Given the size and commercial value of commercial print runs, often producing tens of thousands or more printed products, it is crucial that these initial approval processes are to the satisfaction to all participants. Accordingly, the importance of the approval process cannot be overstated. As a result, it is common for a representative of a customer to attend at the premises of the printer for this approval process. As printers and customers alike may be located anywhere in the world, significant amounts of travel (with attendant costs, lost time performing other duties, inconvenience, risk, etc) can be involved in effectively concluding these necessary approval processes.
In addition, it will be appreciated that the visual assessment of a press pull as compared to a contract proof can involve an element of subjectivity. The individual responsible for making that subjective assessment thus faces a huge responsibility to ensure that his or her decision as to the satisfactory nature of the press pull is a sound one. Because of the need to be physically present for the approval process, only a limited number of customer representatives (often only one or two) are involved in the approval process—in spite of the fact that preferably more persons should be involved so as to reduce dependence on the subjective nature of the assessment.
A large print run can require a significant amount of time. In many cases, the customer's representative(s) will not stay on the premises of the printer for the entire print run, Over the course of a long print run, it is possible, if not likely, that one or more printing variables may change. It is not uncommon to find that the last printed product in a long print run looks significantly different from the original press pull and the contract proof. The slow degradation of the printing process as compared to the contract proof can be problematic. A printer itself may remove representative specimens as they are printed (i.e. take additional press pulls) and make comparisons to the contract proof. However, the printer's assessment of the printed product may not be as critical as the customer's assessment. Thus, failure to monitor printing processes throughout the print run can lead to disputes between a customer and a printer.
In an effort to address some of the above problems in a convenient if not entirely trustworthy or accurate manner, some persons will compare a press pull against the electronic soft proof displayed on a video monitor. The problem of course is that video monitors do not necessarily accurately or consistently display colour and such comparisons can be unreliable. Attempts have been made to make such a process more reliable by ensuring that the video monitor has been calibrated to an industry standard. Nevertheless, it can still be difficult to effectively compare a hard copy press pull against the electronic soft proof (which is not the actual defined standard) on a video screen.
The present invention provides a proofing system and method for analyzing the colour quality of a printed product as compared to a contract proof, which can be used by a printer to more conveniently yet reliably monitor the progress of a print run and by a customer to remotely yet reliably approve initiation of a print run and, if desired, monitor same on a regular or ongoing basis.